1. Field of the Invention
This invention relates to fermentation processes for the production of food yeasts. More particularly, it relates to fermentation processes for the production of pseudomycelial yeasts.
2. Description of the Prior Art
In recent years, much attention has been directed toward the development of new sources of protein which can be incorporated in foods or food additives suitable for human consumption. Rapid increases in world population have made the continued dependence on traditional sources of protein highly impractical. Moreover, the supply of protein from typical sources of protein, such as animal meat and certain vegetables, is inadequate to provide balanced diets sufficient to satisfy the needs of humans throughout the world.
One possible solution to the problem of supplying the ever-increasing need for food protein is provided by processes for the bio-synthetic manufacture of protein through the growth of microorganisms on hydrocarbons or other substrates. It is known, for example, that microorganisms such as bacteria, fungi, and yeast, which are grown by single-cell reproduction, contain high proportions of proteins and can be utilized directly in foods as a whole cell material or can be treated to recover protein concentrate and protein isolate.
With the development of successful processes for the fermentation production of protein-containing microorganisms (sometimes referred to herein as single-cell proteins), a need has developed for methods of texturizing such single-cell protein materials in a manner sufficient to render them suitable alone or in combination with plant and/or animal proteins for use in food products.
Generally, single-cell proteins are initially produced as an aqueous slurry and then subsequently converted into dry powder form, generally having a particle size of about 325 mesh. This dry powder, similar in appearance and feel to flour, lacks the texture and food-like sensation in the mouth necessary to make an attractive food and often imparts a mushy texture to the food into which it is incorporated. Moreover, when placed in water, agglomerated particles of single-cell protein rapidly revert back to single-cell form.
One solution for improving the texture of the yeast in food products is to produce a yeast product having a larger particle size. A type of yeast which meets this requirement is pseudomycelial yeast, which is a multi-cell variant of the more common single-cell variety. The pseudomycelial yeasts are actually clusters of single-cell yeasts which may contain hundreds of individual cells, thus having a particle size much greater than the typical single-cell yeast. These larger pseudomycelial yeasts have superior texturization properties than their single-cell counterparts and also are easier to separate and recover from the fermentation broth because of their greater mass.
Accordingly, it is an object of this invention to provide a process for selectively producing a yeast product containing the pseudomycelial variant of Candida utilis.
A further object of this invention is to provide a process which encourages pseudomycelial cell development and reduces bacterial contamination. These and other objects of this invention will become apparent upon further reading of this specification.